# Copyright 2010-2011 Google
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""
Cryptoarithmetic puzzle

First attempt to solve equation CP + IS + FUN = TRUE
where each letter represents a unique digit.

This problem has 72 different solutions in base 10.

Use of SolutionCollectors.
Use of Solve().
Use of gflags to choose the base.
"""

import gflags, sys
from constraint_solver import pywrapcp
from os import abort

FLAGS = gflags.FLAGS
gflags.DEFINE_integer('base', 10, "Base used to solve the problem.")
gflags.DEFINE_bool('print_all_solutions', False, "Print all solutions?")

def CPIsFun():
  # Constraint programming engine
  solver = pywrapcp.Solver('CP is fun!');
  
  kBase = gflags.FLAGS.base
  
  # Decision variables
  digits = range(0, kBase)
  digits_without_zero = digits[1:]

  c = solver.IntVar(digits_without_zero, 'C');
  p = solver.IntVar(digits, 'P');
  i = solver.IntVar(digits_without_zero, 'I');
  s = solver.IntVar(digits, 'S');
  f = solver.IntVar(digits_without_zero, 'F');
  u = solver.IntVar(digits, 'U');
  n = solver.IntVar(digits, 'N');
  t = solver.IntVar(digits_without_zero, 'T');
  r = solver.IntVar(digits, 'R');
  e = solver.IntVar(digits, 'E');
  
  # We need to group variables in a list to be able to use
  # the global constraint AllDifferent
  letters = [c, p, i, s, f, u, n, t, r, e]
  
  # Check if we have enough digits
  assert kBase >= len(letters)

  # Constraints
  solver.Add(solver.AllDifferent(letters))
  
  # CP + IS + FUN = TRUE
  term1 = solver.Sum([kBase*c, p])
  term2 = solver.Sum([kBase*i, s])
  term3 = solver.Sum([kBase*kBase*f, kBase*u, n])
  sum_terms = solver.Sum([term1, term2, term3])
  
  sum_value = solver.Sum([kBase*kBase*kBase*t, kBase*kBase*r, kBase*u, e])
  solver.Add(sum_terms == sum_value)
  
  all_solutions = solver.AllSolutionCollector()
  # Add the interesting variables to the SolutionCollector
  all_solutions.Add(letters)
  
  db = solver.Phase(letters, solver.INT_VAR_DEFAULT,
                             solver.INT_VALUE_DEFAULT)
  solver.Solve(db, all_solutions)
  
  # Retrieve the solutions
  numberSolutions = all_solutions.SolutionCount()
  
  print "Number of solutions: ", numberSolutions
  
  if (gflags.FLAGS.print_all_solutions):
    for index in range(numberSolutions):
      print "C=", all_solutions.Value(index, c), " P=", all_solutions.Value(index, p), " I=", \
      all_solutions.Value(index, i), " S=", all_solutions.Value(index, s), " F=", all_solutions.Value(index, f), \
      " U=", all_solutions.Value(index, u), " N=", all_solutions.Value(index, n), " T=", all_solutions.Value(index, t), \
      " R=", all_solutions.Value(index, r), " E=", all_solutions.Value(index, e)
   
  return

if __name__ == '__main__':
  try:
    FLAGS(sys.argv)  # parse flags
  except gflags.FlagsError, e:
    print '%s\\nUsage: %s ARGS\\n%s' % (e, sys.argv[0], FLAGS)
    sys.exit(1)
  CPIsFun()
